What is achalasia?

Achalasia: A Primary Esophageal Motility Disorder

Achalasia is a primary esophageal motility disorder characterized by impaired lower esophageal sphincter (LES) relaxation and absent peristalsis in the esophageal body, resulting in progressive dysphagia, regurgitation, and chest pain. 1 This condition cannot be cured, but treatments aim to relieve symptoms, improve esophageal emptying, and prevent the development of megaesophagus.

Pathophysiology and Etiology

Achalasia results from inflammation of the myenteric plexus leading to aganglionosis, with evidence supporting an autoimmune component in its pathogenesis 1. The condition is characterized by:

• Destruction of inhibitory neurons in the esophageal myenteric plexus
• Failure of LES relaxation during swallowing
• Loss of coordinated peristalsis in the esophageal body

Potential triggers include:

• Viral infections (including SARS-CoV-2)
• Chagas disease (particularly in patients with travel history to Central/South America)
• Autoimmune conditions (associated with systemic sclerosis, Addison's disease)
• Paraneoplastic manifestations (associated with lymphoma, lung cancer, breast cancer)

Classification

According to the Chicago Classification, achalasia is categorized into three subtypes based on high-resolution manometry findings 2:

• Type I (Classic): Non-compression subtype with a decompensated, dilated esophagus
• Type II: Pan-esophageal compression, presumed to be the precursor to type I
• Type III (Spastic): Associated with persistent peristalsis with spasm (previously known as vigorous achalasia)

Type II is the most common presenting subtype and has the best response to therapy, followed by type I, while type III responds poorly to all treatments 2, 1.

Clinical Presentation

Common symptoms include:

• Dysphagia for both solids and liquids
• Regurgitation of undigested food
• Chest pain
• Weight loss
• Less specific symptoms: heartburn, chronic cough, aspiration pneumonia

Diagnosis

The gold standard for diagnosis is high-resolution manometry (HRM), which demonstrates:

• Absent peristalsis
• Impaired LES relaxation
• Elevated integrated relaxation pressure (IRP)

Other diagnostic methods include:

• Barium esophagram (shows dilated esophagus with "bird's beak" narrowing at LES)
• Endoscopy (to rule out mechanical obstruction or malignancy)

Diagnostic challenges include:

• No definitive biomarker exists for achalasia
• The condition evolves over time, making early diagnosis difficult
• IRP can be less than the upper limit of normal in some achalasia cases, particularly in type I 2

Treatment Options

Treatment decisions should be based on achalasia subtype, local expertise, therapeutic availability, and patient choice 2:

1. Per-Oral Endoscopic Myotomy (POEM):

   • First-line therapy for type III achalasia 2
   • Comparable to laparoscopic Heller myotomy for all achalasia subtypes 2
   • Should be performed by experienced physicians in high-volume centers (20-40 procedures needed to achieve competence) 2
   • Post-POEM patients have high risk of developing reflux esophagitis 2

2. Laparoscopic Heller Myotomy (LHM):

   • Usually combined with partial fundoplication
   • Overall success rate of 87% 3
   • Best candidates are young patients, especially men 3

3. Pneumatic Dilation:

   • Overall success rate of 78% 3
   • Best response in women and older patients 3
   • Anticipate repeat dilations over the years 2

4. Other Treatments:

   • Botulinum toxin injection into the LES
   • Smooth muscle relaxants (calcium channel blockers, nitrates)
   • Usually reserved for older patients or those with co-morbid illness 3

Treatment Considerations by Subtype

• Type I and II: Both pneumatic dilation and LHM are highly efficacious; POEM is also effective but may cause more reflux 2
• Type III: POEM is preferred, with myotomy length calibrated to the spastic segment 2
• EGJ outflow obstruction: May resolve spontaneously (20-40% of cases); if treated, consider as type II achalasia 2

Prognosis and Follow-up

The prognosis for achalasia patients to return to near-normal swallowing is good, but the disease is rarely "cured" with a single procedure, and intermittent touch-up procedures may be required 3. Post-treatment monitoring should include:

• Surveillance for reflux symptoms, especially after POEM
• Consideration of proton pump inhibitor therapy and/or surveillance endoscopy 2
• Monitoring for late complications including megaesophagus and increased risk of esophageal carcinoma

Common Pitfalls and Caveats

• Achalasia is often misdiagnosed before HRM due to esophageal shortening and pseudorelaxation 2
• Type III achalasia is frequently mistaken for esophageal spasm before HRM 2
• EGJ outflow obstruction can mimic achalasia but may have different etiologies requiring thorough evaluation 2
• Delay in diagnosis may occur when symptoms mimic gastroesophageal reflux disease 4